Fluid control apparatus

ABSTRACT

There is an apparatus for regulating air flow into a rim mounted pneumatic vehicle tyre. The apparatus has an elongated valve housing  1  with an inlet end  1 A, an outlet end  2  and a central portion between the outlet and inlet. The outlet end includes a rim insertion portion  3  configured to fit into an aperture in the tyre rim. There is a pistion  8  disposed within the housing. The piston includes a valve member  19 . A coil spring  22  acts between the housing and piston so that in use of the apparatus the piston is biased to a open position for passage of air into the tyre and is movable against the spring bias under air pressure build-up in the tyre to a closed position at which the valve member seals against a valve seat. The spring acts in tension and the piston and spring are located in the central portion of the housing clear of the rim insertion portion. The rim insertion portion is of a reduced size not obstructive to the mounting of the tyre.

FIELD OF THE INVENTION

[0001] This invention relates to fluid control devices More particularlyalthough not exclusively it discloses an improved pressure cutoff valvefor vehicle tyres.

BACKGROUND TO THE INVENTION

[0002] Correct pressure in vehicle tyres is of considerable importance.Excessive pressure can cause premature tread wear and loss of tractionin the wet. Low pressure on the other hand can cause loss of stabilitywhen cornering and tyre failure from excessive wall flexing. While mostservice stations provide facilities for drivers to check their tyres thegauges are often defective or at best inaccurate. In order to alleviatesuch problems valves have been proposed for tyres which during fillingautomatically cut off the air supply once a preset pressure is reached.The user therefore does not need to be concerned about monitoring tyrepressure during filling. Rather it is only necessary to maintain the airhose fitting on the tyre valve until it automatically cuts off. Thesevalves typically use a piston which is biased to an open position by acompression spring during filling but is moved against said bias to aclosed position when an applied force from the internal tyre pressurereaches a preset amount of say 200 kpa. Existing valves have thedisadvantage however that the compression spring and piston are locatedin the base of the valve assembly which is therefore enlarged andprotrudes a substantial distance through into the interior of the tyrerim. This obstructs the fitting of the tyre and can result in the baseof the valve housing being damaged during initial inflation as the tyrebead expands onto the rim.

SUMMARY OF THE INVENTION

[0003] It is therefore an object of this invention to ameliorate theaforementioned disadvantage and accordingly a apparatus for regulatingair flow into a rim mounted pneumatic vehicle tyre is disclosed, saidapparatus having an elongated valve housing with an inlet end, an outletend and a central portion, the outlet end including a rim insertionportion configured to fit into an aperture in the tyre rim, a pistondisposed within said housing and including a valve member, a coil springacting between said housing and piston whereby in use of said apparatusthe piston is biased to an open position for passage of air into saidtyre and is movable against said bias under force of air pressurebuild-up in said tyre to a closed position at which the valve memberseals against a valve seat to close off said passage of air wherein thespring acts in tension and said piston is located within said centralportion of the housing clear of the rim insertion portion so that saidrim insertion portion is of a reduced size not to obstruct the mountingof said tyre.

[0004] Preferably said piston is fitted with a visual indicator to showposition.

[0005] It is further preferred that the valve housing be fitted with aschrader type one way valve at the inlet end.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The currently preferred embodiment of this invention will now bedescribed with reference to the attached drawings in which:-

[0007]FIG. 1 is a perspective side view of an automobile tyre valveaccording to the invention,

[0008]FIG. 2 is a vertical cross-sectional of the valve of FIG. 1 whenin the open position, and

[0009]FIG. 3 is a cross-sectional view along the lines A-A of FIG. 1.

[0010]FIG. 4 is a cross-sectional view similar to FIG. 2 but with thevalve in the closed position, and

[0011]FIG. 5 is a cross-sectional view of a spring tension adjustmentplug which can be fitted to the valve of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0012] Referring first to FIGS. 1 and 2 the valve housing 1 may comprisean elongated cylindrical casing with an inlet 1A at the top as shown andan outlet 2 at the bottom. The outlet end of the housing preferablycomprise an insertion sleeve 3 with a groove 4 and shoulder 5 whichadapt said sleeve for fitting through an aperture in a pneumatic tyrerim 5A. Preferably the outlet end is moulded from rubber or othersuitable material to obtain the necessary pressure tight seat to the rimAt the inlet end 1A there is a short pipe section 6 of reduced diameterto connect with an air supply hose nozzle such as that provided atservice stations Immediately below this is a transparent cap 7 throughwhich the position of an internal indicator band can be viewed asdescribed later.

[0013] Referring more specifically to FIGS. 2 and 3 there is a piston 8which is longitudinally slidable between the housing cylinder wall 9 anda central tube 10. The tube 10 is part of a sub-assembly which includesthe pipe 6 with a schrader type inlet valve 11 of known construction.This sub-assembly is threaded into or otherwise rigidly connected to thehousing at 12. The transparent cap 7 also fits onto the housing at thislocation and provides a view window between the top of said housing 12Aand the pipe 6. As the pipe 6 and housing are fixed relative to oneanother this cap 7 takes no load and can therefore be of nonstructuralmaterial such as a low cost plastic. There are O-rings 13, 14 fitted toprovide a sliding pressure tight fit between both the outside of piston8 and cylinder 9 as well as the internal piston bore 15 and tube 10.Preferably a directional low friction cup seal 16 may also be fittedinto a nich 17 in the piston immediately below O-ring 13 to furtherensure against air leakage between the piston and cylinder. The piston 8at its upper end mounts the indicator band 18 and towards the lower endthe bore 15 is fitted with a valve member having a bevelled head 19 andupwardly directed needle 20. The needle extends up through a seat 21formed at the base of tube 10. The seat is shaped to form a pressuretight seal when engaged by the bevelled head 19 of the valve member.There is also a tension spring 22 which acts between a transverse pin 23located across the housing just above the insertion sleeve and thecentre 24 of the piston. Preferably the spring at one end hooks over pin23 and at the other end seats in spiral grooves around the centre of thepiston. In FIG. 2 the piston is held to its lowermost position where theband 18 abuts the top of the housing. In accordance with this inventionit will be noted that the tension spring 22 and piston 8 move within thecentre portion of the housing above the insertion sleeve 3. This allowsthe rim insertion sleeve at the outlet end to be greatly reduced indiameter and length. It therefore provides virtually no obstruction tothe tyre bead during initial mounting and inflation of said tyre on therim. The moulded rubber construction of the insertion sleeve with thecurrent embodiment also allows the housing 1 to flex relative to thetyre rim to reduce the chances of breakage.

[0014] In the open position of FIG. 2 a supply of pressurised air isable to flow through the inlet schrader valve 11, down through tube 10,around open valve member 19, through ports 26, along clearance space 27between the spring 22 and housing to enter the tyre (not shown) throughoutlet 2. As the pressure inside the tyre builds up however a force(arrow B) acts against the underside of the piston moving it upward. Ata preset cutoff pressure of say 200 kpa determined by the underside areaof the piston 8, the deflection constant of the spring 22 and theposition of valve seat 21 the upward displacement of the piston 8 causesthe valve head 19 to close into said seat as shown in FIG. 4. This cutsoff further air flow into the tyre. It will also be noted from FIG. 4that the band 18 simultaneously moves upward within transparent cap 7 toindicate that the preset pressure has been reached in the tyre and thecutoff valve 19 is closed. If tyre pressure subsequently falls belowthis preset pressure the piston and indicator band. 18 move downwardlyunder the tension force of spring 22 to show low pressure and the valve19 opens in preparation for filling. Leakage of air out of the tyrehowever is prevented by the one way operation of the schrader valve 11which only allows discharge through deliberate depression of insert stem2B.

[0015] As an alternative to the fixed transverse pin 23 for holding thelower end of the spring 22 a threaded anchor plug 29 as shown incross-section by FIG. 5 may be turned into the housing at the samelocation. This plug has an upstanding pin 30 with a circumferentialgroove 31. The lower end of the spring is then shaped to seat in thisgroove so that rotation of the plug using an allen key or the Like onsocket 32 adjusts the spring tension and thus the cutoff pressure of thevalve. A series of apertures 33 around the periphery of the plug allowsair to pass through to the outlet 2.

[0016] It will thus be appreciated that this invention at least in theform of the embodiment disclosed provides a novel and useful improvementto vehicle tyre valves. Clearly however the example described is onlythe currently preferred form of the invention and a wide variety ofmodifications may be made which would be apparent to a person skilled inthe art. For example the shape and configuration of the transparent capand the preset cutoff pressure may be changed according to application.Also while it is currently preferred to construct the valve and housingfrom a corrosion resistant metal such as brass the invention extends tothe use of any other suitable material.

[0017] For the purposes of this specification expressions such as “top”,“bottom”, “below”, “upper” and “lower” etc refer to the valve housing inone position of use as illustrated are are not to be taken asnecessarily limiting.

1. Apparatus for regulating air flow into a rim mounted pneumaticvehicle tyre, said apparatus having an elongated valve housing with aninlet end, an outlet end and a central portion, the outlet end includinga rim insertion portion configured to fit into an aperture in the tyrerim, a piston disposed within said housing and including a valve member,a coil spring acting between said housing and piston whereby in use ofsaid apparatus the piston is biased to an open position for passage ofair into said tyre and is movable against said bias under force of airpressure build-up in said tyre to a closed position at which the valvemember seals against a valve seat to close off said passage of airwherein the spring acts in tension and said piston and spring arelocated within said central portion of the housing clear of the riminsertion portion so that said rim insertion portion is of a reducedsize not-obstructive to the mounting of said tyre.
 2. The apparatus asclaimed in claim 1 wherein a visual indicator is fitted to the piston toshow the position thereof.
 3. The apparatus as claimed in claim 2wherein the visual indicator is a band which is visible through atransparent cap fitted to the housing.
 4. The apparatus as claimed inclaim 3 wherein in use of said apparatus the cap carries no structuralload and is made of moulded plastic.
 5. The apparatus as claimed inclaim 4 wherein said spring acts between a pin located at the outlet endof said housing and a centre part of said piston.
 6. A apparatus asclaimed in claim 5 wherein the piston is slidable along a central tubeand cylinder wall in said housing, said tube being part of asub-assembly which is connected to said housing.
 7. The apparatus asclaimed in claim 6 wherein the piston at an upper end thereof mountssaid band and towards the lower end thereof carries said valve membershaped to form a pressure tight seal when engaged in the valve seatlocated at the base of said central tube.
 8. The apparatus as claimed inclaim 7 wherein the inlet end is fitted with a schrader valve.
 9. Theapparatus as claimed in claim 8 wherein the rim insertion portionincludes a rubber sleeve with a shoulder and groove into which the edgesof said rim aperture fit.
 10. The apparatus as claimed in claim 9wherein the valve member has a bevelled head and upwardly directedneedle which extends through the valve seat.
 11. The apparatus asclaimed in claim 10 wherein the valve housing includes a transparent capthrough which an internal indicator can be viewed to show the positionof said piston.
 12. The apparatus as claimed in claim 11 wherein saidcap carries no structure load during the operation of the valve.